This invention relates to a fuel evaporating device adapted for use in the complete evaporation of fuel to be fed to an engine.
In fuel evaporating devices which are now in wide use, the fuel is apt to fail to be atomized completely, with the result that a considerable amount of fuel in a droplet form is fed along the wall surface of an air intake manifold to an engine. Such an incomplete evaporating condition of a mixture gas is not desirable, because such a mixture gas is responsible for atmospheric pollution due to detrimental exhaust gas from an engine. On the other hand, there has been proposed an attempt whereby to utilize the heat of exhaust gas for heating an air intake manifold for the purpose of enhancing the atomization of a mixture gas. However, this attempt suffers from a disadvantage in that, due to its arrangement heating only a part of an air intake pipe, the temperature rise in the exhaust gas due to continuing driving of a car directly leads to a temperature rise in the air intake pipe, such that the temperature of intake air to be fed to an engine is raised, thus lowering the charging efficiency and the efficiency of operation or running of an engine. In addition, uncontrolled heating of an air intake pipe results in neglecting an optimum evaporating temperature of fuel and eventually in hindering satisfactory prevention of atmospheric pollution due to exhaust gases. In addition, in the starting time of an engine, particularly in winter time or in cold districts, the mere use of exhaust gas for heating an air intake pipe will not present a solution to the incomplete evaporation of fuel. Furthermore, the complete evaporation of fuel is mandatory for solving atmospheric polution due to exhaust gas particularly in the case of a lean mixture gas, and it is further required to this end that a mixture of fuel and air be maintained at a constant atomized condition throughout the entire operational range of an engine. It is least true that an attempt to maintain an optimum temperature for the evaporation of fuel has not been proposed, nor has been paid a consideration for the variation in intake pressure during the phases from the starting time to the high speed operating condition of an engine.